Re-think of solving the gloving problem in bolting systems by adulterating steel particles

Abstract

Resin cartridge is the most widely used bolt supporting material in coal mines; its superiority in applying active and prestressed support to loose rock is well acknowledged. Mastic and catalyst inside a resin cartridge are separately enveloped in polyester film. This film, in most circumstances, is unlikely to be completely broken into pieces; then, the bolt will be wrapped by the film, leading to the terminology of ‘gloving’. Gloving has been puzzling coal mine practitioners for many years; its influences on the mechanical properties of bolting systems are still unknown and no consistent conclusion has been established yet. In this study, the effectiveness of adulterating steel particles into the resin cartridge, as raised by some existing literature, was experimentally rediscussed. A total of 78 tests were conducted to test the shredding effects of steel particles by adulterating them into resin cartridges. Specimens prepared by a bolt/cable installation machine highly restored the in situ installation process, during which the revolving speed and the torque of motor were recorded. Then, pullout tests and gloving observations were conducted to clarify the effectiveness of the particles in terms of the mechanical improvement capacity and gloving removing capacity, and the mechanism of gloving and unmixed resin was analyzed explicitly. The results showed that adulterating particles with a specific size and ratio into resin could improve the loading performance of the bolting system, but that was not always the case. Gloving and unmixed resin were major factors that led to deviations and weakened the loading capacity, and the effectiveness of particle adulteration exhibited evident randomness. Furthermore, in most circumstances, gloving and unmixed resin, regardless of the particle sizes, could not be erased by simply mixing the resin cartridge and steel particles.